Pyrolysis is the chemical decomposition of organic materials by heating in the absence of oxygen or other reagents (other than water vapor in some cases). Pyrolysis can be used to convert complex materials such as biomass or waste into substances that are either desirable or less harmful. For example, pyrolysis can be used to convert biomass (such as lignocellulosic biomass) into pyrolysis oil (sometimes referred to as “bio-oil”).
Pyrolysis oil is generally a mixture of water, light volatiles, and non-volatiles. Pyrolysis oil is highly reactive because of the presence of significant quantities of oxygen. As a combustible material, pyrolysis oil has many potential uses.
However, pyrolysis oil cannot be used as a fuel in internal combustion engines without further processing. Amongst other problems, pyrolysis oil is generally immiscible with petroleum-based diesel fuel. Also, the pyrolysis oil is highly acidic, with a pH of 1.5-3.8. This acidity, and along with the substantial water content, can lead to corrosion problems. In addition, the cetane number of pyrolysis oil is typically far too low.
Current approaches for utilizing pyrolysis oil in diesel engines include the formation of pyrolysis oil/diesel emulsions. However, such emulsions can be relatively expensive to make and may not have desirable levels of shelf-stability.